Tunability of photoluminescent properties and energy transfer behaviour of thermally stable BaZr(PO4)2: Dy3+, Eu3+ phosphor for warm white LEDs and indoor lighting applications

In the present work solid state reaction route has been employed to synthesize Dy³⁺ doped and Dy³⁺/Eu³⁺ co-doped BaZr(PO₄)₂ (BZP) phosphor samples. The X-Ray diffraction studies revealed formation of pure phase with monoclinic crystal structure. The Photoluminescent studies of BZP: Dy³⁺ featured emission peaks at 482 nm and 576 nm thus leading to emission in white region. Further, the co-doping of phosphor with Eu⁺ supplements the spectrum with a red component at 612 nm thus shifting the correlated color temperature (CCT) from cooler to warmer region. The variation in relative concentration of Dy³⁺ and Eu³⁺ ions along with the variation in excitation wavelength generate tunable photoluminescent properties. The energy transfer mechanism between Dy³⁺ and Eu³⁺ has been studied using Dexter and Riesfeld's theory which revealed that interactions responsible for energy transmission from Dy³⁺ to Eu³⁺ are dipole-dipole in nature.The BZP phosphor coactivated with Dy³⁺ and Eu³⁺ retained 87.87 % of luminous intensity at 420 K and possesses activation energy value of 0.267 eV thus demonstrating excellent thermal stability. The thermal stability and flexible color tunability of the co-activated BZP phosphor makes it a befitting contender for utilization in white light emitting diodes.